Chapter 7 - Circular Motion and Gravitation - Learning Path Questions and Exercises - Exercises - Page 262: 43

a). $v=\sqrt (2gL)$ b). $T=3mg$

a). By law of conservation of energy, Potential energy = Kinetic energy $mgL=\frac{1}{2}mv^{2}$ So, $v=\sqrt (2gL)$ b). At lowermost point, tension will be equal to sum of weight + centrifugal force. $T=mg+m\frac{v^{2}}{L}=mg+2mg=3mg$